The present invention relates generally to the field of electric motor drives such as those used to control electric motors and similar loads. More particularly, the present invention relates to systems and methods for using switched converters to rectify alternating current (AC) into direct current (DC), boost the overall voltage of a DC bus, and provide for regenerative braking capabilities while reducing the number of components in the system.
Power rectifier systems are used in a wide range of applications. For example, power converters that perform rectification are used with centrifuges, magnetic clutches, pumps and more generally, in electric motor drive controllers to rectify and condition incoming AC voltage and to supply DC voltage to the motor. Many electric motor controllers also include some type of motor braking ability, in which energy from the motor is re-converted while slowing the driven load. The energy resulting from the braking operation can either be fed into a resistor, which will convert the energy into heat, or fed back into the supply network. Electric motor controllers with regenerative braking ability can feed the energy back into the supply network. This regenerative braking ability is very useful in reducing energy usage and in decreasing operational costs. Electric motor drives may also provide for the ability to boost DC voltage during certain low-voltage conditions such as sagging line voltage, motor starting, and heavy motor loading. The added boost in DC voltage during these periods allows for maintaining normal operating conditions and also increases the life of the motor. However, one drawback of electric motor drives that provide for motor drive, regenerative braking, and DC voltage boosting is that they require many extra components, lose energy due to constant switching activity, and are costly.